The present invention relates to a method for treating a weft knitted fabric containing a regenerated cellulose fiber, as well as to a weft knitted fabric.
Weft knitted fabrics containing a regenerated cellulose fiber have had a problem in that they tend to generate weft bar owing to the variation in configuration and color difference and, as a result, become a product of strikingly low quality.
Hence, investigation has been made on knitting conditions, or, it has been attempted to minimize the variation in yarn quality, or, inspection of weft bar has been made at the stage of gray fabric. However, with the control of knitting conditions and yarn quality alone, it is impossible to prevent the generation of weft bar; further, even if weft bar is at a level giving substantially no problem, in the inspection of gray fabric, the weft bar often appears after dyeing. Nevertheless, no effective means has been found which can eliminate or prevent weft bar.
For improvement of the appearance of cellulose fiber fabric, there is disclosed, in WO 95/24524, mercerization of a fabric comprising a Lyocell fiber. This treatment comprises treating said fabric under tension in an aqueous solution containing a high concentration (10 to 30% by weight) of sodium hydroxide. The treatment aims at improving the appearance of said fabric, particularly the appearance of its surface having friction marks which looks like being covered with frost. In applying this treatment to a regenerated cellulose fiber, however, there has been a problem in that striking reduction in strength takes place, the treated fabric is impaired, its hand is hardened, and the appearance is impaired strikingly.
WO 97/8370 relates to a Lyocell fiber multifilament yarn and the improvement of wrinkles of a fabric comprising the yarn, and discloses treating said fiber under tension in a swelling agent or solvent containing said fiber in a concentration of 50 to 150 g/liter (about 4.8 to 13.1% by weight). In treating a regenerated cellulose fiber by this method, however, there has been a problem in that reduction in strength takes place, the hand becomes hard, and the properties and appearance of the fiber are impaired strikingly.
JP-A-6-166956 relates to a woven fabric or knitted fabric of a regenerated cellulose/polyester composite yarn and a method for production thereof, and discloses untwisting said woven fabric or knitted fabric by a relaxation treatment and then applying an alkali treatment to allow the regenerated cellulose fiber in the woven fabric or knitted fabric to generate fibril. In the production method of JP-A-6-166956, there are descriptions of xe2x80x9cThe relaxation treatment is conducted at 100 to 135xc2x0 C. for 2 to 60 minutes using a jet dyeing machinexe2x80x9d and xe2x80x9cThe alkali treatment is necessary for reducing the polyester fiber moiety by 3 to 30% by weight, and in Examples, an alkali treatment is conducted with an aqueous solution containing, for example, 2.8, 4.1 or 14.7 g/liter of sodium hydroxide, using a jet dyeing machinexe2x80x9d. Judging from these descriptions, it is apparent that the alkali treatment is conducted in a rope state and not in a spread state.
With this method, there is obtained no effect of setting a regenerated cellulose fiber in a strain-free state, and no effect for improvement of bar is expectable.
In JP-A-8-291470 is described a method for prevention of friction marks, which comprises subjecting, to an alkali treatment, a cellulose fiber spun using an organic solvent or a fabric of the cellulose fiber in its spread state and then treating the resulting fiber or fabric with an aqueous solution containing a glyoxal type resin. In the literature, there is a description of xe2x80x9cThe alkali treatment is conducted with an aqueous alkaline solution containing 50 to 90 g/liter of sodium hydroxide, at 5 to 60xc2x0 C. for 20 seconds to 2 minutes in a spread statexe2x80x9d. However, the literature makes no mention of mellowing treatment in the method for production of the fiber or fabric.
Regarding the prevention and elimination of the weft bar which appears easily in weft knitted fabrics containing a regenerated cellulose fiber, there is no description in any of WO 95/24524, WO 97/8370, JP-A-6-166956 and JP-A-8-291470; and no solution is given by any conventional technique. Thus, weft knitted fabrics containing a regenerated cellulose fiber have a problem in practical application.